1. Field of the Invention
This invention relates to a method and an apparatus for correlating target track data by which a decision is made as to whether or not a plurality of target track data are correlated with each other.
2. Description of the Prior Art
A multisensor system such as a radar surveillance system for air traffic control and the like requires a target track data correlation processing by which a decision is made as to whether or not tracking data transmitted from plural sensor sites are data on the same target.
FIG. 1 shows an example of an air traffic control system as a multisensor system. Numerals 1A and 1B denote radar apparatus. 2A and 2B denote tracking apparatus which execute a tracking processing using radar observation data, and which produce the result of tracking as tracking data (punctual coordinates of a flying object: X, Y, Z; velocities: X, Y). 3 denotes a surveillance apparatus which executes a correlation processing for the tracking data transmitted from the radar sites and decides whether the tracking data are data on the same flying target or not. Since each tracking data has a tracking error, respectively, they may not have the same value even if they are data on the same flying target. Therefore, a correlation processing on tracking data has been made in the surveillance apparatus 3 in accordance with the processes shown in FIGS. 2 and 3. It is assumed that values of the position and velocity of the tracking data transmitted from a sensor site A are (X.sub.1, Y.sub.1, Z.sub.1) and (X.sub.1, Y.sub.1), respectively while these values from a sensor site B are (X.sub.2, Y.sub.2, Z.sub.2) and (X.sub.2, Y.sub.2). The system of FIG. 2 decides whether or not differences of position data in the directions of X, Y and Z coordinates, .vertline.X.sub.1 -X.sub.2 .vertline., .vertline.Y.sub.1 -Y.sub.2 .vertline. and [.vertline.Z.sub.1 -Z.sub.2 .vertline. and a velocity difference in a XY plane .vertline.(X.sub.1.sup.2 +Y.sub.1.sup.2)-(X.sub.2.sup.2 +Y.sub.2.sup.2).vertline. are within allowable errors .epsilon..sub.1, .epsilon..sub.2 , .epsilon..sub.3 and .epsilon..sub.4 (blocks 21, 22, 23 and 24). And if all of these differences are within the allowable errors, the above two tracking data are judged as ones on the same flying target (block 25). On the other hand, the system of FIG. 3 provides a mark or score P.sub.1 (block 28) when the position differences in the directions of X and Y coordinates are smaller than threshold values .epsilon..sub.1 and .epsilon..sub.2, respectively (block 27), scores P.sub.2 and P.sub.3 (blocks 31 and 32) when the height and velocity differences are smaller than the threshold values .epsilon..sub.3 and .epsilon..sub.4 (blocks 29 and 30) and a further score P.sub.4 (block 34) when the target attendant information data coincide with each other (block 33). And, if the summed scope P is larger than a predetermined value S (block 35), the tracking data are judged as being on the same flying target (block 36).
However, these prior art systems don't take account of density distributions of parameters of target track data to be compared and therefore, cannot obtain a high success rate in the correlation processing.